The thermoplastic polyester resin is used in a wide range of fields such as machine mechanism components, electrical and electronic components and automobile components by taking advantage of its characteristics, for example, excellent injection moldability and mechanical properties. The thermoplastic polyester resin is, however, likely to deteriorate the mechanical strength by heat aging at high temperature. For the use as the industrial material for machine mechanism components, electrical and electronic components and automobile components, the thermoplastic polyester resin needs to have long-term heat aging resistance at high temperature, in addition to balance of general chemical characteristics and general physical characteristics. In recent years, there has also been a growing demand for reduction of thickness and weight, accompanied with downsizing of a molded article. Especially, in the application of thin-walled molded articles such as a connector, generation of a large amount of cracked gas from a material in the molding process leads to generation of air bubbles in the molded article and thereby causes molding failures such as reduction of mechanical strength and poor appearance. Accordingly, there is a demand for a material having a small amount of cracked gas generation and excellent molding processability.
In order to improve the thermal stability of the thermoplastic polyester resin, proposed techniques include a thermoplastic resin composition obtained by blending a compound having an isocyanato group and/or carbodiimide group with a polybutylene terephthalate resin (for example, Patent Literature 1) and a thermoplastic resin composition obtained by blending a multivalent alcohol, a reinforcing material and a polymer reinforcing agent with a thermoplastic resin selected from the group consisting of polyamides, polyesters and their mixtures (for example, Patent Literature 2).
These proposed techniques still have problems of insufficient heat aging resistance and mechanical properties and an increased gas generation amount in the molding process.
A thermoplastic resin composition obtained by blending a multivalent hydroxyl compound and an epoxy compound with a polyester resin (for example, Patent Literature 3) has also been proposed.